Consolidated Balance Sheet - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Current Assets [Abstract]
Cash and Cash Equivalents	$ 203.1	$ 69.1
Accounts Receivable (Less Allowance of $1.1 and $1.7)	87.4	144.4
Inventories – Net	78.2	86.7
Prepayments and Other	28.6	34.1
Total Current Assets	397.3	334.3
Property, Plant and Equipment – Net	4,062.9	3,904.4
Regulatory Assets	391.2	389.5
Equity Investments	160.2	161.1
Goodwill and Intangible Assets – Net	1.1	223.3
Other Non-Current Assets	163.8	152.4
Total Assets	5,176.5	5,165.0
Current Liabilities [Abstract]
Accounts Payable	150.4	149.8
Accrued Taxes	41.3	51.4
Accrued Interest	17.7	17.9
Long-Term Debt Due Within One Year	27.7	57.5
Other	59.5	128.5
Total Current Liabilities	296.6	405.1
Long-Term Debt	1,505.9	1,428.5
Deferred Income Taxes	213.5	223.6
Regulatory Liabilities	508.8	512.1
Defined Benefit Pension and Other Postretirement Benefit Plans	163.9	177.3
Other Non-Current Liabilities	282.8	262.6
Total Liabilities	2,971.5	3,009.2
Commitments, Guarantees and Contingencies (Note 7)
Shareholders’ Equity [Abstract]
Common Stock Without Par Value, 80.0 Shares Authorized, 51.7 and 51.5 Shares Issued and Outstanding	1,433.3	1,428.5
Accumulated Other Comprehensive Loss	(26.9)	(27.3)
Retained Earnings	798.6	754.6
Total Shareholders’ Equity	2,205.0	2,155.8
Total Liabilities and Shareholders' Equity	$ 5,176.5	$ 5,165.0